Spectral imagery has emerged in the past decade as one of the most powerful tools for a range of remote sensing problems including defeating camouflage, remote identification of chemical and biological compounds, and anomaly detection. Spectral imagery can take on many forms. For example, two-color infrared spectral imagery is useful for applications such as locating recently disturbed earth. In another example, multi-spectral imagery (MSI) are designed to have a small number (e.g., 3-15) of spectrally distinct bands in the visible, near infrared (IR), and mid IR range and with minimal overlap in their spectral responses. Some MSI systems utilize spatially separate focal plane arrays (FPAs) to measure each spectral band, which leads to increased system cost and results in large data volumes that make storage and transmission of data challenging in real time.
Other than near IR and mid IR portions, the long-wave-IR (LWIR) portion of spectrum has also been the focus of specific efforts, because objects near room temperature tend to be emissive rather than reflective in this wavelength range. This allows thermal imaging to be largely independent of illumination conditions, which may cause all the IR imaging “black and white” with no spectral content.
The human eye is a sensor that can elegantly represent a dynamic scene by extracting enormous visual information. The human eye uses a paradigm where the foveous of the eye is populated by three classes of cones, often referred to as the long—(L), middle—(M), and short—(S) wavelength sensitive cones. Unlike typical MSI bands, the L, M, and S cones have spectral responses with extremely high correlations (ρLM=0.91, ρLS=0.097, ρMS=0.18, where ρ is the correlation coefficient). The eye compensates for this redundancy by initially decorrelating the responses of the individual receptors through weighted combinations of the receptor outputs. A consequence of this processing is that the relative importance of the combination channels are not equal, with the vast majority of the information being transmitted in the achromatic channel, and much less in the two chromatic channels with one including a red-green difference and the other including a blue-yellow difference.
Thus, there is a need to overcome these and other problems of the prior art and to provide a retinal system that operates in long-wave IR region similarly to the human eye operating in the visible spectral range and brings “color” to the IR range.